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A caponier

A caponier is a type of fortification in a defensive structure, the word originates from the French word caponnière.[1]

In some types of bastioned fortifications, the caponier served only as a covered means of access to the outworks, with the bastion-trace allowing for the defence of the ditch by fire from the main parapets.


Rifle port inside a caponier, Fort Napoleon, Ostend, Belgium.

Originally the term referred to a covered passageway that traversed the ditch outside the curtain of a fortress. Fire from this point could cover the ditch between the ravelin and the curtain wall to deter any attempt to storm the wall,[2] thus the passageway was equipped with musket ports and cannon ports that fired along the ditch.

While fortifications were evolving to the simpler polygonal style, the term was sometimes used to describe the flanking positions set at the corners of the ditch that provide the same function in that style of fort, especially in France.

It usually takes the form of a low passage, often partly sunken into the floor of the ditch and projecting outward into it, with access from the main fortress via a passage through the curtain wall, or as fortresses became largely underground, via a tunnel from within the fort, the roof is vulnerable to plunging fire, and is sometimes thick and curved to deflect falling shells, or covered with a thick layer of earth. Some, however were open-topped.


A caponier covered with a layer of earth, Sacavém Fort, Portugal.

The caponier is usually equipped with a firing step and rifle ports to allow troops to fire along the ditch, and often has provision for small cannon to sweep the ditch as well. To clear the smoke and fumes from the firing the roof of the caponier is often provided with ventilation ports.

To avoid fire from one caponier bearing on the next, caponiers are usually set at alternate corners of the fort, so that they fire towards a blank wall at the opposite end of the ditch, giving full coverage of the ditch without subjecting the next caponier to fire, the length of the straight sections of the ditch is chosen so that it can be covered by fire from a single caponier. Caponiers are often wedge shaped so that they can fire down both angles of the ditch.

Counterscarp battery[edit]

An alternative to the caponier is a counterscarp battery, dug into the outer face of the corner of the ditch, giving a similar field of fire. Again reached by a tunnel from within the fort, it does not have the vulnerable roof that the caponier has, but being outside the ditch, is potentially more vulnerable to mining. Both structures may be found in the same fort.

Locations of caponiers[edit]

Interior of caponier at Fort de Bois l'Abbé

Caponiers are a common feature of 18-[3] and 19th-century fortifications, and are found on almost all the Victorian forts of Malta, the Palmerston Forts in UK, the Lisbon Entrenched Camp forts in Portugal, fortifications in many Nordic countries, and in:


See also[edit]


  1. ^ Wikisource-logo.svg Chisholm, Hugh, ed. (1911). "Caponier". Encyclopædia Britannica (11th ed.). Cambridge University Press. 
  2. ^ Stocqueler, Joachim (1853). "The military encyclopaedia: a technical, biographical, and historical dictionary". Google Books. W.H. Allen & Co. Retrieved 2017-04-23. 
  3. ^ a b c d "Remains of Capinier - Birgu" (PDF). National Inventory of the Cultural Property of the Maltese Islands (1525). 28 June 2013. Archived from the original (PDF) on 14 July 2015. 

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